1. Field of the Invention
The present invention relates to a drive device, a method of controlling strain and a computer readable medium storing a program.
2. Description of Related Art
Recent years, the need for the technology to detect strain which occurs in a drive unit as typified by an actuator is growing. For example, in the case of a robot hand, the amount of strain needs to be strictly controlled for gripping an object more properly and accurately. Thus, a unit for detecting strain of a drive unit is necessary. Presently, electrical-type strain gages are major units for detecting strain. An electrical-type strain gauge is a mechanical sensor which can calculate the amount of strain by measuring the change of electrical resistance due to a deformation.
As an example of an electrical-type strain gauge, a technique is disclosed which reduces measurement errors to enable high precision uniaxial displacement measurement (for example, refer to JP H07-321385 A).
Also, a technique is disclosed which reduces the influence caused by the operation of an actuator to improve the detection accuracy of a sensor (for example, refer to JP 2011-072180 A).
In the techniques described in JP H07-321385 A and JP 2011-072180 A, a sensor is attached to a drive unit to detect the strain of the drive unit and the strain of the drive unit is controlled based on the detected value.
In order to detect strain, there is also a method called a moire method. In the moire method, a grid pattern is drawn on the surface of the drive unit, and strain is detected by carrying out an image analysis with respect to the change of the grid pattern.
In general, when strain of a drive unit is detected, transmitting the detected information on strain to a signal processing unit causing as small time lag as possible is important. Also, since a drive unit frequently undergoes impact resulting from external force or the like, countermeasure against impact is necessary. As described above, rapid detection and high impact resistance are required to a section for detecting strain in a drive unit.
However, in the prior art, there is no detection unit which satisfies the two performances described above (rapid detection and high impact resistance) at the same time.
For example, electrical-type strain gauges described in JP H07-321385 A and JP 2011-072180 A can detect strain rapidly. However, since these strain gauges are formed to be very fragile not to disrupt driving, they have low impact resistance and easy to be broken.
In case where moire method is adopted, since a grid pattern is directly inscribed on a drive body, high impact resistance can be expected. However, since carrying an image analysis takes time, there is a problem that detection rate is low.